It's functional in that people can get from point A to point B when they need to. Flights aren't prohibitively expensive enough to push people to take the tax increase. A flight from Minneapolis to Chicago is like $100-$200, and for the rare occurrence someone needs that specific route, it's not that expensive to pay for.

Don't get me wrong, we'd be much better off with a national rail network connecting major cities. But Americans are some of the most cost-averse voters, both on the left and right. And you're looking at a multi-billion dollar project for something like a Chicago to NYC line. The citizens of Illinois and NYC aren't keen to take the tax hike. Fed won't pay for it since it only benefits 2 specific voter bases and doesn't do anything to swing an election (Dems win those cities anyway, Republicans will never take them over even if they funded rail).